Providing estimated accuracy of mobile station synchronization and mobile station transmission offset to the network

ABSTRACT

A mobile station (MS), a base station subsystem (BSS), and various methods are described herein that enable a positioning node (e.g., Serving Mobile Location Center (SMLC)) to improve the accuracy of estimating a position of the mobile station.

CLAIM OF PRIORITY

This application is a divisional of U.S. patent application Ser. No.15/799,037 filed on Oct. 31, 2017, which claims the benefit of priorityto U.S. Provisional Application Ser. Nos. 62/415,990, 62/419,794, and62/433,672 respectively filed on Nov. 1, 2016, Nov. 9, 2016, and Dec.13, 2016. The entire contents of these documents are hereby incorporatedherein by reference for all purposes.

RELATED PATENT APPLICATIONS

This application is related to the co-filed U.S. patent application Ser.Nos. 15/798,928 and 15/798,952, each entitled “Providing EstimatedAccuracy of Mobile Station Synchronization to the Network”, each ofwhich claim the benefit of priority to U.S. Provisional Application Ser.No. 62/415,990, filed on Nov. 1, 2016. The entire contents of thesedocuments are hereby incorporated herein by reference for all purposes.

TECHNICAL FIELD

The present disclosure relates generally to the wirelesstelecommunications field and, more particularly, to a mobile station(MS), a base station subsystem (BSS), and various methods that enable apositioning node (e.g., Serving Mobile Location Center (SMLC)) toimprove the accuracy of estimating a position of the mobile station.

BACKGROUND

The following abbreviations are herewith defined, at least some of whichare referred to within the following description of the presentdisclosure.

-   3GPP 3rd-Generation Partnership Project-   APDU Application Protocol Data Unit-   AGCH Access Grant Channel-   ASIC Application Specific Integrated Circuit-   BSS Base Station Subsystem-   BBSLAP Base Station Subsystem Location Services Assistance Protocol-   BSSMAP Base Station Subsystem Mobile Application Part-   BSSMAP-LE BSSMAP-Location Services Extension-   BTS Base Transceiver Station-   CN Core Network-   DSP Digital Signal Processor-   EC Extended Coverage-   EC-AGCH Extended Coverage Access Grant Channel-   EC-GSM Extended Coverage Global System for Mobile Communications-   EC-PDTCH Extended Coverage-Packet Data Traffic Channel-   EC-RACH Extended Coverage-Random Access Channel-   EC-SCH Extended Coverage-Synchronization Channel-   EDGE Enhanced Data rates for GSM Evolution-   EGPRS Enhanced General Packet Radio Service-   eMTC Enhanced Machine Type Communications-   eNB Evolved Node B-   FCCH Frequency Correction Channel-   GSM Global System for Mobile Communications-   GERAN GSM/EDGE Radio Access Network-   GPRS General Packet Radio Service-   IE Information Element-   IoT Internet of Things-   LAC Location Area Code-   LTE Long-Term Evolution-   MCC Mobile Country Code-   MME Mobility Management Entity-   MNC Mobile Network Code-   MS Mobile Station-   MTA Multilateration Timing Advance-   MTC Machine Type Communications-   NB-IoT Narrow Band Internet of Things-   PDN Packet Data Network-   PDU Protocol Data Unit-   PLMN Public Land Mobile Network-   RACH Random Access Channel-   RAN Radio Access Network-   RLC Radio Link Control-   SCH Synchronization Channel-   SGSN Serving GPRS Support Node-   SMLC Serving Mobile Location Center-   TA Timing Advance-   TBF Temporary Block Flow-   TLLI Temporary Logical Link Identifier-   TS Technical Specification-   TSG Technical Specification Group-   UE User Equipment-   UL Uplink-   UMTS Universal Mobile Telephony System-   WCDMA Wideband Code Division Multiple Access-   WiMAX Worldwide Interoperability for Microwave Access

At the 3rd-Generation Partnership Project (3GPP) Technical SpecificationGroup (TSG) Radio Access Network (RAN) Meeting #72, a Work Item on“Positioning Enhancements for GERAN” was approved (see RP-161260; Busan,Korea; 13-16 Jun. 2016—the contents of which are hereby incorporatedherein by reference), wherein one candidate method for realizingimproved accuracy when determining the position of a mobile station (MS)is timing advance (TA) multilateration (see RP-161034; Busan, Korea;13-16 Jun. 2016—the contents of which are hereby incorporated herein byreference), which relies on establishing the MS position based on TAvalues in multiple cells.

At the 3GPP TSG-RAN1 Meeting #86, a proposal based on a similar approachwas made also to support positioning of Narrow Band Internet of Things(NB-IoT) mobiles (see R1-167426; Gothenburg, Sweden; 22-26 Aug. 2016—thecontents of which are hereby incorporated herein by reference).

TA is a measure of the propagation delay between a base transceiverstation (BTS) and the MS, and since the speed by which radio wavestravel is known, the distance between the BTS and the MS can be derived.Further, if the TA applicable to the MS is measured within multiple BTSsand the positions of these BTSs are known, the position of the MS can bederived using the measured TA values. The measurement of the TA requiresthat the MS synchronize to each neighbor BTS and transmit a signaltime-aligned with the estimated timing of the downlink channel receivedfrom each BTS. The BTS measures the time difference between its own timereference for the downlink channel, and the timing of the receivedsignal (transmitted by the MS). This time difference is equal to twotimes the propagation delay between the BTS and the MS (one propagationdelay of the BTS's synchronization signal sent on the downlink channelto the MS, plus one equal propagation delay of the signal transmitted bythe MS back to the BTS).

Once the set of TA values are established using a set of one or moreBTSs during a given positioning procedure, the position of the MS can bederived through so called multilateration wherein the position of the MSis determined by the intersection of a set of hyperbolic curvesassociated with each BTS (see FIG. 1). The calculation of the positionof the MS is typically carried out by a serving positioning node (i.e.,serving Serving Mobile Location Center (SMLC)), which implies that allof the derived TA and associated BTS position information needs to besent to the positioning node (i.e., the serving SMLC) that initiated thepositioning procedure.

Referring to FIG. 1 (PRIOR ART) there is shown a diagram of an exemplarywireless communication network 100 used to help explain a problemassociated with the traditional multilateration process in determining aposition of a mobile station 102 (MS 102). The exemplary wirelesscommunication network 100 has several nodes which are shown and definedherein as follows:

-   -   Foreign BTS 104 ₃: A BTS 104 ₃ (shown as foreign BTS3 104 ₃)        associated with a BSS 106 ₃ (shown as non-serving BSS3 106 ₃)        that uses a positioning node 108 ₂ (shown as non-serving SMLC2        108 ₂) that is different from a positioning node (shown as        serving SMLC1 108 ₁) which is used by the BSS 106 ₁ (shown as        serving BSS1 106 ₁) that manages the cell serving the MS 102        when the positioning (multilateration) procedure is initiated.        The derived TA information (TA3 114 ₃) and identity of the        corresponding cell are relayed by the BSS 106 ₃ (shown as        non-serving BSS3 106 ₃), the SGSN 110 (core network), and the        BSS 106 ₁ (shown as serving BSS1 106 ₁) to the serving        positioning node (shown as serving SMLC1 108 ₁) (i.e., in this        case the non-serving BSS3 106 ₃ has no context for the MS 102).        The BSS 106 ₃ (shown as non-serving BSS3 106 ₃) can be        associated with one or more BTSs 104 ₃ (only one shown) and a        BSC 112 ₃ (shown as non-serving BSC3 112 ₃).    -   Local BTS 104 ₂: A BTS 104 ₂ (shown as local BTS2 104 ₂)        associated with a BSS 106 ₂ (shown as non-serving BSS2 106 ₂)        that uses the same positioning node 108 ₁ (shown as serving        SMLC1 108 ₁) as the BSS 106 ₁ (shown as serving BSS1 106 ₁) that        manages the cell serving the MS 102 when the positioning        (multilateration) procedure is initiated. The derived TA        information (TA2 114 ₂) and identity of the corresponding cell        are relayed by the BSS 106 ₂ (shown as non-serving BSS2 106 ₂)        and the BSS 106 ₁ (shown as serving BSS1 106 ₁) to the serving        positioning node (shown as serving SMLC1 108 ₁) (i.e., in this        case the non-serving BSS2 106 ₂ has no context for the MS 102)        (i.e., inter-BSS communications allows the non-serving BSS2 106        ₂ to relay the derived TA information (TA2 114 ₂) and the        identity of the corresponding cell to the serving BSS1 106 ₁).        The BSS 106 ₂ (shown as non-serving BSS2 106 ₂) can be        associated with one or more BTSs 104 ₂ (only one shown) and a        BSC 112 ₂ (shown as non-serving BSC2 112 ₂).    -   Serving BTS 104 ₁: A BTS 104 ₁ (shown as serving BTS1 104 ₁)        associated with a BSS 106 ₁ (shown as serving BSS1 106 ₁) that        manages the cell serving the MS 102 when the positioning        (multilateration) procedure is initiated. The derived TA        information (TA1 114 ₁) and identity of the corresponding cell        are sent directly by the BSS 106 ₁ (shown as serving BSS1 106 ₁)        to the serving positioning node 108 ₁ (shown as serving SMLC1        108 ₁) (i.e., in this case the serving BSS1 106 ₁ has a context        for the MS 102). The BSS 106 ₁ (shown as serving BSS1 106 ₁) can        be associated with one or more BTSs 104 ₁ (only one shown) and a        BSC 112 ₁ (shown as serving BSC1 112 ₁).    -   Serving SMLC 108 ₁: The SMLC 108 ₁ (shown as serving SMLC1 108        ₁) that commands the MS 102 to perform the positioning        (multilateration) procedure (i.e., the SMLC 108 ₁ sends a Radio        Resource Location services Protocol (RRLP) Multilateration        Request to the MS 102).    -   Serving BSS 106 ₁: The BSS 106 ₁ (shown as serving BSS1 106 ₁)        associated with the serving BTS 104 ₁ (shown as serving BTS1 104        ₁) (i.e., the BSS 106 ₁ that has context information for the        Temporary Logical Link Identity (TLLI) corresponding to the MS        102 for which the positioning (multilateration) procedure has        been triggered).    -   Non-serving BSS 106 ₂ and 106 ₃: A BSS 106 ₃ (shown as        non-serving BSS3 106 ₃) associated with a foreign BTS 104 ₃        (shown as foreign BTS3 104 ₃) and a BSS 106 ₂ (shown as        non-serving BSS2 106 ₂) associated with a local BTS 104 ₂ (shown        as local BTS2 104 ₂) (i.e., the BSSs 106 ₂ and 106 ₃ do not have        context information for the TLLI corresponding to the MS 102 for        which the positioning (multilateration) procedure has been        triggered).

Note 1: FIG. 1 is an illustration of an exemplary multilaterationprocess involving three BTSs 104 ₁, 104 ₂, and 104 ₃ associated withthree timing advance (TA) values 114 ₁, 114 ₂, 114 ₃ for a particular MS102. The multilateration can involve more than three BTSs 104 ₁, 104 ₂,and 104 ₃ and more than three TA values 114 ₁, 114 ₂, 114 ₃.

Note 2: FIG. 1 is an illustration of an exemplary wireless communicationnetwork 100 showing the basic nodes which are needed to explain thepositioning (multilateration) process. It should be appreciated that theexemplary wireless communication network 100 includes additional nodeswhich are well known in the art.

It is advantageous for the serving SMLC 108 ₁ to estimate the accuracyof the estimated position of the MS 102. The accuracy of the estimatedposition of the MS 102 depends on the number of cell specific TAestimates 114 ₁, 114 ₂, 114 ₃ (for example) it has been provided with,the accuracy of the individual (cell specific) TA estimates 114 ₁, 114₂, 114 ₃ (for example) performed by the BTSs 104 ₁, 104 ₂, 104 ₃ (forexample) as well as the MS-BTS geometry, i.e., the true position of theMS 102 relative to the involved BTSs 104 ₁, 104 ₂, 104 ₃ (for example).The accuracy of the TA estimation performed by a BTS 104 ₁, 104 ₂, 104 ₃in turn depends on the accuracy by which the MS 102 is able to time itsuplink (UL) transmissions to the BTS 104 ₁, 104 ₂, 104 ₃ according tosignals received from the BTS 104 ₁, 104 ₂, 104 ₃ (i.e., the MSTransmission Timing Accuracy), and the accuracy by which the BTS 104 ₁,104 ₂, 104 ₃ is able to measure the timing of signals received from theMS 102 (i.e., the BTS Timing Advance Accuracy). The accuracy by whichthe MS 102 is able to time its uplink transmissions to the BTS 104 ₁,104 ₂, 104 ₃ according to signals received from the BTS 104 ₁, 104 ₂,104 ₃ may be specified as a worst-case tolerance. For example, a GlobalSystem for Mobile telephony (GSM) MS 102 is required to time its uplinktransmission to the BTS 104 ₁, 104 ₂, 104 ₃ signal with a tolerance of±1.0 symbol period (a symbol period being 48/13 μs), see 3GPP TechnicalSpecification (TS) 45.010 V13.3.0 (2016 September)—the contents of thisdisclosure are incorporated herein by reference—from which the excerptbelow is taken:

-   -   “The MS shall time its transmissions to the BTS according to        signals received from the BTS. The MS transmissions to the BTS,        measured at the MS antenna, shall be 468,75-TA normal symbol        periods (i.e. 3 timeslots-TA) behind the transmissions received        from the BTS, where TA is the last timing advance received from        the current serving BTS. The tolerance on these timings shall be        ±1 normal symbol period.”

One problem with the existing solution is that the serving SMLC 108 ₁does not have any information about the TA estimation accuracy of theBTS 104 ₁, 104 ₂, 104 ₃ or about the actual accuracy with which the MS102 is able to time its uplink transmission to the BTS 104 ₁, 104 ₂, 104₃ according to signals received from the BTS 104 ₁, 104 ₂, 104 ₃. If theserving SMLC 108 ₁ receives cell specific TA information as determinedby the BTS 104 ₁, 104 ₂, 104 ₃ and assumes that the accuracy by whichthe MS 102 is able to time its uplink transmission to the BTS 104 ₁, 104₂, 104 ₃ according to signals received from the BTS 104 ₁, 104 ₂, 104 ₃for that cell is according to the specified worst case tolerance, theestimated accuracy of the estimated position of the MS 102 may be overlypessimistic. Therefore, services requiring a higher positioning accuracymay not be provided with a positioning estimate (i.e., the serving SMLC108 ₁ may conclude that it cannot realize the target positioningaccuracy) even though the actual positioning accuracy may in fact bebetter than estimated and therefore sufficient. Alternatively, theserving SMLC 108 ₁ may involve more BTSs 104 ₁, 104 ₂, 104 ₃ than arenecessary in the positioning process in order to guarantee sufficientaccuracy in the estimated position of the MS 102. These problems andother problems are addressed by the present disclosure.

SUMMARY

A mobile station, a base station subsystem (BSS) and various methods foraddressing the aforementioned problems are described in the independentclaims. Advantageous embodiments of the mobile station, the BSS and thevarious methods are further described in the dependent claims.

In one aspect, the present disclosure provides a mobile stationconfigured to interact with a BSS, wherein the BSS includes a BTS. Themobile station comprises a processor and a memory that storesprocessor-executable instructions, wherein the processor interfaces withthe memory to execute the processor-executable instructions, whereby themobile station is operable to perform a receive operation, an estimateoperation, and a transmit operation. In the receive operation, themobile station receives, from the BSS, a multilateration request. In theestimate operation, the mobile station in response to the receipt of themultilateration request (i) estimates a synchronization accuracy withthe BTS, and (ii) estimates a transmission offset for uplinktransmissions to the BTS. In the transmit operation, the mobile stationtransmits, to the BSS, a RLC data block that includes at least (i) aTLLI of the mobile station, (ii) the estimated synchronization accuracy,and (iii) the estimated transmission offset (note: the BSS subsequentlyrelays this information to the SMLC). An advantage of the mobile stationperforming these operations is that it enables a SMLC to make a betterestimate of the accuracy of the estimated position of the mobilestation. In addition, for the case where the mobile station does notperform these operations, the BSS can provide the SMLC with the mobilestation's transmission timing accuracy capability information receivedfrom the SGSN, thus allowing the SMLC to make an a priori assessment asto how many BTSs may be needed to reach the desired position accuracyand thus provide the mobile station with more accurate assistanceinformation.

In another aspect, the present disclosure provides a method in a mobilestation that is configured to interact with a BSS, wherein the BSSincludes a BTS. The method comprises a receiving step, an estimatingstep, and a transmitting step In the receiving step, the mobile stationreceives, from the BSS, a multilateration request. In the estimatingstep, the mobile station in response to receiving the multilaterationrequest (i) estimates a synchronization accuracy with the BTS and (ii)estimates a transmission offset for uplink transmissions to the BTS. Inthe transmitting step, the mobile station transmits, to the BSS, a RLCdata block that includes at least (i) a TLLI of the mobile station, (ii)the estimated synchronization accuracy, and (iii) the estimatedtransmission offset (note: the BSS subsequently relays this informationto the SMLC). An advantage of the mobile station performing these stepsis that it enables a SMLC to make a better estimate of the accuracy ofthe estimated position of the mobile station. In addition, for the casewhere the mobile station does not perform these steps, the BSS canprovide the SMLC with the mobile station's transmission timing accuracycapability information received from the SGSN, thus allowing the SMLC tomake an a priori assessment as to how many BTSs may be needed to reachthe desired position accuracy and thus provide the mobile station withmore accurate assistance information.

In yet another aspect, the present disclosure provides a BSS whichincludes a BTS and is configured to interact with a mobile station. TheBSS further comprises a processor and a memory that storesprocessor-executable instructions, wherein the processor interfaces withthe memory to execute the processor-executable instructions, whereby theBSS is operable to perform a transmit operation and a receive operation.In the transmit operation, the BSS transmits, to the mobile station, amultilateration request. In the receive operation, the BSS receives,from the mobile station, a RLC data block that includes at least (i) aTLLI of the mobile station, (ii) an estimated mobile stationsynchronization accuracy, and (iii) an estimated mobile stationtransmission offset (note: the BSS subsequently relays this informationto the SMLC). An advantage of the BSS performing these operations isthat it enables a SMLC to make a better estimate of the accuracy of theestimated position of the mobile station. In addition, for the casewhere the BSS does not perform these operations, the BSS can provide theSMLC with the mobile station's transmission timing accuracy capabilityinformation received from the SGSN, thus allowing the SMLC to make an apriori assessment as to how many BTSs may be needed to reach the desiredposition accuracy and thus provide the mobile station with more accurateassistance information.

In still yet another aspect, the present disclosure provides a method ina BSS which includes a BTS and is configured to interact with a mobilestation. The method comprises a transmitting step and a receiving step.In the transmitting step, the BSS transmits, to the mobile station, amultilateration request. In the receiving step, the BSS receives, fromthe mobile station, a RLC data block that includes at least (i) a TLLIof the mobile station, (ii) an estimated mobile station synchronizationaccuracy, and (iii) an estimated mobile station transmission offset(note: the BSS subsequently relays this information to the SMLC). Anadvantage of the BSS performing these steps is that it enables a SMLC tomake a better estimate of the accuracy of the estimated position of themobile station. In addition, for the case where the BSS does not performthese steps, the BSS can provide the SMLC with the mobile station'stransmission timing accuracy capability information received from theSGSN, thus allowing the SMLC to make an a priori assessment as to howmany BTSs may be needed to reach the desired position accuracy and thusprovide the mobile station with more accurate assistance information.

Additional aspects of the present disclosure will be set forth, in part,in the detailed description, figures and any claims which follow, and inpart will be derived from the detailed description, or can be learned bypractice of the invention. It is to be understood that both theforegoing general description and the following detailed description areexemplary and explanatory only and are not restrictive of the presentdisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present disclosure may be obtainedby reference to the following detailed description when taken inconjunction with the accompanying drawings:

FIG. 1 (PRIOR ART) is a diagram of an exemplary wireless communicationnetwork used to help explain a problem associated with the traditionalmultilateration process in determining a position of a mobile station;

FIG. 2 is a diagram of an exemplary wireless communication network whichincludes a SGSN, multiple SMLCs, multiple BSSs, and a mobile stationwhich are configured in accordance with an embodiment of the presentdisclosure;

FIG. 3 is a diagram used to describe a MS Transmission Offset which iscalculated by the mobile station in accordance with an embodiment of thepresent disclosure;

FIG. 4 is a diagram illustrating one possible coding of a MSsynchronization accuracy field which contains the mobile stationestimated assessment of the BTS timing (i.e., the mobile stationsynchronization accuracy) in accordance with an embodiment of thepresent disclosure;

FIG. 5 is a diagram illustrating one possible coding of a MSTransmission Offset field which contains the MS Transmission Offset thatthe mobile station was forced to apply due to the transmissionopportunities corresponding to the internal time base of the mobilestation in accordance with an embodiment of the present disclosure;

FIG. 6 illustrates details of a BSSMAP-LE PERFORM LOCATION REQUESTmessage with a MS Transmission Timing Accuracy Capability IE inaccordance with an embodiment of the present disclosure;

FIG. 7 illustrates details of the MS Transmission Timing AccuracyCapability IE in accordance with an embodiment of the presentdisclosure;

FIGS. 8A-8B illustrate details of a MS Radio Access Capability IE whichincludes the MS Transmission Timing Accuracy Capability IE in accordancewith an embodiment of the present disclosure;

FIG. 9 is a diagram that illustrates a Multilateration TA (MTA) IE whichincludes an overall BTS TA accuracy in accordance with an embodiment ofthe present disclosure;

FIG. 10 is a flowchart of a method implemented in the mobile station inaccordance with an embodiment of the present disclosure;

FIG. 11 is a block diagram illustrating a structure of the mobilestation configured in accordance with an embodiment of the presentdisclosure;

FIG. 12 is a flowchart of a method implemented in the BSS in accordancewith an embodiment of the present disclosure; and

FIG. 13 is a block diagram illustrating a structure of the BSSconfigured in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

A discussion is provided herein first to describe an exemplary wirelesscommunication network 200 that includes multiple BSSs 202 ₁, 202 ₂, 202₃, a mobile station 204, and multiple SMLCs 206 ₁ and 206 ₂ configuredto improve the accuracy in estimating a position of the mobile station204 in accordance with an embodiment of the present disclosure (see FIG.2). Then, a discussion is provided to disclose various techniques thatthe BSSs 202 ₁, 202 ₂, 202 ₃, and the mobile station 204 can use toenable the serving SMLC 206 ₁ to improve the accuracy in estimating aposition of the mobile station 204 in accordance with differentembodiments of the present disclosure (see FIGS. 3-9). Thereafter, adiscussion is provided to explain the basicfunctionalities-configurations of the mobile station 204 and the BSSs202 ₁, 202 ₂, 202 ₃, each of which are configured to improve theaccuracy in which the serving SMLC 206 ₁ can estimate a position of themobile station 204 in accordance with different embodiments of thepresent disclosure (see FIGS. 10-13).

Exemplary Wireless Communication Network 200

Referring to FIG. 2, there is illustrated an exemplary wirelesscommunication network 200 in accordance with the present disclosure. Thewireless communication network 200 includes a core network (CN) 208(which comprises at least one CN node 207 (e.g., SGSN 207)), multipleSMLCs 206 ₁ and 206 ₂, and multiple BSSs 202 ₁, 202 ₂, 202 ₃, (onlythree shown) which interface with a mobile station 204 (only one shown)(note: in practice there would be multiple mobile stations 204 but forclarity only one mobile station 204 is discussed herein). The wirelesscommunication network 200 also includes many well-known components, butfor clarity, only the components needed to describe the features of thepresent disclosure are described herein. Further, the wirelesscommunication network 200 is described herein as being a GSM/EGPRSwireless communication network 200 which is also known as an EDGEwireless communication network 200. However, those skilled in the artwill readily appreciate that the techniques of the present disclosurewhich are applied to the GSM/EGPRS wireless communication network 200are generally applicable to other types of wireless communicationsystems, including, for example, EC-GSM, WCDMA, LTE, and WiMAX systems.

The wireless communication network 200 includes the BSSs 202 ₁, 202 ₂,202 ₃ (which are basically wireless access nodes 202 ₁, 202 ₂, 202 ₃,RAN nodes 202 ₁, 202 ₂, 202 ₃, wireless access points 202 ₁, 202 ₂, 202₃) which can provide network access to the mobile station 204. Each BSS202 ₁, 202 ₂, 202 ₃ includes one or more BTSs 210 ₁, 210 ₂, 210 ₃ and aBSC 212 ₁, 212 ₂, 212 ₃. The BSSs 202 ₁, 202 ₂, 202 ₃ are connected tothe core network 208 and, in particular, to the CN node 207 (e.g., SGSN207). The core network 208 is connected to an external packet datanetwork (PDN) 219, such as the Internet, and a server 213 (only oneshown). The mobile station 204 may communicate with one or more servers213 (only one shown) connected to the core network 208 and/or the PDN219.

The mobile station 204 may be referred to generally as an end terminal(user) that attaches to the wireless communication network 200, and mayrefer to either a Machine Type Communications (MTC) device (e.g., asmart meter) or a non-MTC device. Further, the term “mobile station” isgenerally intended to be synonymous with the term mobile device,wireless device, “User Equipment,” or UE, as that term is used by 3GPP,and includes standalone mobile stations, such as terminals, cell phones,smart phones, tablets, Internet of Things (IoT) devices, cellular IoTdevices, and wireless-equipped personal digital assistants, as well aswireless cards or modules that are designed for attachment to orinsertion into another electronic device, such as a personal computer,electrical meter, etc. . . . .

The mobile station 204 may include a transceiver circuit 214 forcommunicating with the BSSs 202 ₁, 202 ₂, 202 ₃ (RAN nodes 202 ₁, 202 ₂,202 ₃), and a processing circuit 216 for processing signals transmittedfrom and received by the transceiver circuit 214 and for controlling theoperation of the mobile station 204. The transceiver circuit 214 mayinclude a transmitter 218 and a receiver 220, which may operateaccording to any standard, e.g., the GSM/EDGE standard, and the EC-GSMstandard. The processing circuit 216 may include a processor 222 and amemory 224 for storing program code for controlling the operation of themobile station 204. The program code may include code for performing theprocedures as described hereinafter.

Each BTS 210 ₁, 210 ₂, 210 ₃ may include a transceiver circuit 226 ₁,226 ₂, 226 ₃ for communicating with the mobile station 204 (typicallymultiple mobile stations 204—only one shown for clarity) and theirrespective BSC 212 ₁, 212 ₂, 212 ₃, a processing circuit 228 ₁, 228 ₂,228 ₃ for processing signals transmitted from and received by thetransceiver circuit 226 ₁, 226 ₂, 226 ₃ and for controlling theoperation of the corresponding BTS 210 ₁, 210 ₂, 210 ₃. The transceivercircuit 226 ₁, 226 ₂, 226 ₃ may include a transmitter 230 ₁, 230 ₂, 230₃ and a receiver 232 ₁, 232 ₂, 232 ₃, which may operate according to anystandard, e.g., the GSM/EDGE standard, and the EC-GSM standard. Theprocessing circuit 228 ₁, 228 ₂, 228 ₃ may include a processor 234 ₁,234 ₂, 234 ₃, and a memory 236 ₁, 236 ₂, 236 ₃ for storing program codefor controlling the operation of the corresponding BTS 210 ₁, 210 ₂, 210₃. The program code may include code for performing the procedures asdescribed hereinafter.

Each BSC 212 ₁, 212 ₂, 212 ₃ may include a transceiver circuit 238 ₁,238 ₂, 238 ₃ for communicating with their respective BTS 210 ₁, 210 ₂,210 ₃ and SMLC 206 ₁, 206 ₂, a processing circuit 240 ₁, 240 ₂, 240 ₃for processing signals transmitted from and received by the transceivercircuit 238 ₁, 238 ₂, 238 ₃ and for controlling the operation of thecorresponding BSC 212 ₁, 212 ₂, 212 ₃, and a network interface 242 ₁,242 ₂, 242 ₃ for communicating with the SGSN 207 part of the corenetwork 208. The transceiver circuit 238 ₁, 238 ₂, 238 ₃ may include atransmitter 244 ₁, 244 ₂, 244 ₃ and a receiver 246 ₁, 246 ₂, 246 ₃,which may operate according to any standard, e.g., the GSM/EDGE standard(in this example), and the EC-GSM standard. The processing circuit 240₁, 240 ₂, 240 ₃ may include a processor 248 ₁, 248 ₂, 248 ₃, and amemory 250 ₁, 250 ₂, 250 ₃ for storing program code for controlling theoperation of the corresponding BSC 212 ₁, 212 ₂, 212 ₃. The program codemay include code for performing the procedures as described hereinafter.Note: for purposes of the discussion herein, it should be appreciatedthat the BSS 202 ₁, 202 ₂, 202 ₃ circuitry can be considered to be thesame circuitry as BSC 212 ₁, 212 ₂, 212 ₃ (it should be appreciated thata BSS comprises a BSC and a BTS according to well-known prior art, sowhen there is a discussion herein about a BSS performing certainfunctions, it typically means the BSC performing those functions unlessit is specifically mentioned that the BTS is performing a function).

The CN node 207 (e.g., SGSN 207, Mobility Management Entity (MME) 207)may include a transceiver circuit 252 for communicating with the BSSs202 ₁, 202 ₂, 202 ₃, a processing circuit 254 for processing signalstransmitted from and received by the transceiver circuit 252 and forcontrolling the operation of the CN node 207, and a network interface257 for communicating with the PDN 219 or the server 213. Thetransceiver circuit 252 may include a transmitter 256 and a receiver258, which may operate according to any standard, e.g., the GSM/EDGEstandard (in this example), and the EC-GSM standard. The processingcircuit 254 may include a processor 260 and a memory 262 for storingprogram code for controlling the operation of the CN node 207. Theprogram code may include code for performing the procedures as describedhereinafter.

Techniques for Improving Accuracy of Mobile Station's Estimated PositionBRIEF DESCRIPTION

In accordance with an embodiment of the present disclosure, the MS 204when synchronizing to a BTS 210 ₁, 210 ₂, 210 ₃ (three shown) alsoestimates the accuracy 264 ₁, 264 ₂, 264 ₃ by which it has synchronizedto the BTS 210 ₁, 210 ₂, 210 ₃. Further, the MS 204 also estimates a MSTransmission Offset 265 ₁, 265 ₂, 265 ₃ with which it is able to timeits uplink transmissions to the BTS 210 ₁, 210 ₂, 210 ₃. The MS 204reports (e.g., in an uplink Radio Link Control (RLC) data block 270 ₁,270 ₂, 270 ₃) the estimated synchronization accuracy 264 ₁, 264 ₂, 264 ₃and the MS Transmission Offset 265 ₁, 265 ₂, 265 ₃ associated with therespective BTS 210 ₁, 210 ₂, 210 ₃ to the network (e.g., BSS 202 ₁, 202₂, 202 ₃). The BSS 202 ₁, 202 ₂, 202 ₃ (BTS 210 ₁, 210 ₂, 210 ₃) adjustsits estimated TA 271 ₁, 271 ₂, 272 ₃ for the MS 204 according to theindicated MS Transmission Offset 265 ₁, 265 ₂, 265 ₃ and then forwardsin a BSSMAP-LE CONNECTION ORIENTED INFORMATION message 275 ₁, 275 ₂, 275₃ (for example) the Adjusted Estimated Timing Advance 285 ₁, 285 ₂, 285₃ and the estimated MS synchronization accuracy 264 ₁, 264 ₂, 264 ₃ tothe serving SMLC 206 ₁ along with a corresponding BTS Timing AdvanceAccuracy 273 ₁, 273 ₂, 273 ₃. All three of these values 264 ₁, 264 ₂,264 ₃, 273 ₁, 273 ₂, 273 ₃, 285 ₁, 285 ₂, 285 ₃ are taken into accountby the serving SMLC 206 ₁ when estimating the accuracy of the estimatedposition of the MS 204. Alternatively, in another embodiment of thepresent disclosure in order to address scenarios where the MS 204 is notable to provide an estimate of the MS synchronization accuracy 264 ₁ andthe MS Transmission Offset 265 ₁ to the serving SMLC 206 ₁, insteadthere is provided to the serving SMLC 206 ₁ an a priori understanding ofthe MS Transmission Timing Accuracy capability, by having the servingBSS 202 ₁ use a field 266 (MS Transmission Timing Accuracy field 266)which can be added to a MS Radio Access Capability Information Element(IE) 267 and sent to the serving SMLC 206 ₁ (see 3GPP TS 24.008 v14.1.0which discloses the traditional MS Radio Access Capability IE withoutthe new MS Transmission Timing Accuracy field 266—the contents of whichare incorporated herein by reference). The MS Transmission TimingAccuracy field 266 indicates (a) the worst case accuracy (guaranteedminimum accuracy) with which the MS 204 is able to estimate the timingof the BTS 210 ₁ according to signals received from the BTS 210 ₁ and(b) the worst case MS Transmission Offset 265 ₁. It is further proposedin yet another embodiment of the present disclosure that the serving BSS202 ₁ passes either the complete MS Radio Access Capability IE 267 orthe MS Transmission Timing Accuracy field 266 in a BSSMAP-LEPERFORM-LOCATION-REQUEST Protocol Data Unit (PDU) 269 to the servingSMLC 206 ₁ prior to the serving SMLC 206 ₁ triggering multilaterationfor the MS 204 (e.g., sending the MS 204 a multilateration request 272).

Moreover, in order for the serving SMLC 206 ₁ to be able to accuratelyassess the overall MS positioning accuracy, it could also utilize a BTSTA accuracy 271 ₁, 271 ₂, 271 ₃. To this end, it is therefore proposedin another embodiment of the present disclosure to add a means for theBSS 202 ₁, 202 ₂, 202 ₃ to indicate its BTS's TA estimation capability273 ₁, 273 ₂, 273 ₃ to the serving SMLC 206 ₁ in a BSSMAP-LE CONNECTIONORIENTED INFORMATION message 275 ₁, 275 ₂, 275 ₃ either as a new IE oras part of the BSSLAP APDU (note 1: BSS 202 ₁ transmits its BTS TAestimation capability directly to the serving SMLC 206 ₁ within aBSSMAP-LE CONNECTION ORIENTED INFORMATION message 275 ₁; the BSS 202 ₂first transmits its BTS TA estimation capability to the BSS 202 ₁ usinginter-BSS communication, then the BSS 202 ₁ transmits the BSSMAP-LECONNECTION ORIENTED INFORMATION message 275 ₂ to the serving SMLC 206 ₁(this signaling is not shown in FIG. 2); and the BSS 202 ₃ firsttransmits its BTS TA estimation capability to the BSS 202 ₁ using thecore network (e.g., SGSN 207), and the BSS 202 ₁ then transmits theBSSMAP-LE CONNECTION ORIENTED INFORMATION message 275 ₃ to the servingSMLC 206 ₁ (this signaling is not shown in FIG. 2)(note 2: FIG. 2 showsthe direct (logical) transmission of the BSSMAP-LE CONNECTION ORIENTEDINFORMATION MESSAGEs 275 ₂ and 275 ₃ from the BSSs 202 ₂ and 202 ₃ tothe serving SMLC 206 ₁). Alternatively, the BSS 202 ₁, 202 ₂, 202 ₃ (BTS210 ₁, 210 ₂, 210 ₃) may take both the BTS Timing Advance Accuracy 271₁, 271 ₂, 271 ₃ and the MS Sync Accuracy 264 ₁, 264 ₂, 264 ₃ intoaccount and report an overall Timing Advance Accuracy to the SMLC 206 ₁(i.e., the BTS 210 ₁, 210 ₂, 210 ₃ processes the values of the BTSTiming Advance Accuracy 271 ₁, 271 ₂, 271 ₃ and MS Sync Accuracy 264 ₁,264 ₂, 264 ₃ to arrive at a value for the overall Timing AdvanceAccuracy for the corresponding cell which the BTS 210 ₁, 210 ₂, 210 ₃then passes to the SMLC 206 ₁). These embodiments of the presentdisclosure will be discussed in more detail hereinafter.

DETAILED DESCRIPTION

As part of its procedure to time the uplink transmission to the BTS 210₁, 210 ₂, 210 ₃ according to signals received from the BTS 210 ₁, 210 ₂,210 ₃, the MS 204 first synchronizes to the network 200 (BTS 210 ₁, 210₂, 210 ₃). In the synchronization process, the MS 204 estimates thesynchronization accuracy 264 ₁, 264 ₂, 264 ₃ by which it hassynchronized to the BTS 210 ₁, 210 ₂, 210 ₃ (note: the MS 204 willestimate a separate synchronization accuracy 264 ₁, 264 ₂, 264 ₃ foreach BTS 210 ₁, 210 ₂, 210 ₃). For example, the MS 204 can estimate thesynchronization accuracy 264 ₁, 264 ₂, 264 ₃ by performing multiplesynchronizations and measurements of the timing of the BTS 210 ₁, 210 ₂,210 ₃ and estimating the variance between these measurements. Forinstance, if N measurements of the timing are denoted t_(i), i=1, . . ., N, the variance of the individual measurement can be estimated usingthe well-known formula for unbiased sample variance:

$\begin{matrix}{s^{2} = {\frac{1}{N - 1}{\sum\limits_{i = 1}^{N}\; \left( {t_{i} - \overset{\_}{t}} \right)^{2}}}} & \left( {{equation}\mspace{14mu} {{no}.\mspace{14mu} 1}} \right)\end{matrix}$

where t is the mean of t_(i), i.e.,

$\begin{matrix}{\overset{\_}{t} = {\frac{1}{N}{\sum\limits_{i = 1}^{N}\; t_{i}}}} & \left( {{equation}\mspace{14mu} {{no}.\mspace{14mu} 2}} \right)\end{matrix}$

Further, if the MS 204 finally estimates the timing of the BTS 210 ₁,210 ₂, 210 ₃ as the mean of the individual measurements (i.e., by t),the variance of this timing estimate can be estimated by:

$\begin{matrix}{{{var}\left( \overset{\_}{t} \right)} = \frac{s^{2}}{N}} & \left( {{equation}\mspace{14mu} {{no}.\mspace{14mu} 3}} \right)\end{matrix}$

When synchronization is completed, the MS 204 will access the cell.However, the uplink transmission of the MS 204 when accessing the cellmay not be perfectly time aligned with the timing of the signals fromthe BTS 210 ₁, 210 ₂, 210 ₃ as estimated during synchronization due tolimitations in the design of the MS 204. For example, this limitation inthe design of the MS 204 may be due to the internal time base of the MS204 (to which transmissions must be time aligned) which may not beperfectly aligned with the estimated timing of the BTS transmissions.The internal time base used for uplink transmissions may be somewhatarbitrary as to when its corresponding uplink transmission opportunities(see upward pointing dashed arrows in FIG. 3) occur relative to theability of the MS 204 to synchronize to downlink signals (e.g.,Frequency Correction Channel (FCCH)/Synchronization Channel(SCH)/Extended Coverage-Synchronization Channel (EC-SCH)) received fromthe BTS 210 ₁, 210 ₂, 210 ₃. This arbitrariness can be viewed asacceptable as long as the uplink transmission opportunities are spacedtightly enough (e.g., ¼ symbol) such that the worst case known offsetintroduced by the MS 204 when making an uplink transmission will be halfthe spacing of the transmission opportunities (e.g., ⅛ symbol). However,in cases where an enhanced level of positioning accuracy is needed, theoffset imposed by using such an internal time base can still result inlimitations regarding the accuracy with which the SMLC 206 ₁ canestimate the position of the MS 204. It is therefore desirable for theMS 204 to have knowledge of the MS Transmission Offset 265 ₁, 265 ₂, 265₃ it applied when performing the Multilateration Timing Advance (MTA)procedure in a given cell to be made available when the correspondingBSS 202 ₁, 202 ₂, 202 ₃ (BTS 210 ₁, 210 ₂, 210 ₃) attempts to determinethe applicable value of the BTS timing advance 271 ₁, 271 ₂, 271 ₃ forthe MS 204 in that cell.

In other words, by e.g., the BSS 202 ₁, 202 ₂, 202 ₃ (BTS 210 ₁, 210 ₂,210 ₃) not having access to MS Transmission Offset 265 ₁, 265 ₂, 265 ₃applicable when the MS 204 performed the MTA procedure in a given cell,there will be a forced misalignment of uplink transmissions that the BSS202 ₁, 202 ₂, 202 ₃ (BTS 210 ₁, 210 ₂, 210 ₃) will not be able to takeinto account. This will then contribute to the total TA estimation error(i.e., the BSS 202 ₁, 202 ₂, 202 ₃ (BTS 210 ₁, 210 ₂, 210 ₃) willdetermine a value for the Estimated Timing Advance 271 ₁, 271 ₂, 271 ₃but will not be able to determine a value for the Adjusted EstimatedTiming Advance 285 ₁, 285 ₂, 285 ₃). See FIG. 3 where this problem isillustrated with the assumption that the uplink transmissionopportunities associated with the used internal time base are spaced ¼symbol apart. Based on signals from the BTS 210 ₁, 210 ₂, 210 ₃ (i.e.,BTS true timing), the MS 204 estimates the downlink (DL) timing denotedas MS estimated DL timing. Now, due to limitations in the MS 204 (i.e.,the internal time base imposed on all uplink transmissions) there is adifference between the MS Nominal UL Transmission opportunity (e.g.,determined according to the MS estimated DL timing+3 time slot offsetfor the uplink) and the MS Selected Transmission opportunity (i.e., theclosest internal time base uplink transmission opportunity which mayoccur either before or after the MS Nominal Transmission opportunity),denoted MS Transmission Offset 265 ₁, 265 ₂, 265 ₃. The presentdisclosure addresses this problem by having the MS 204 estimate andtransmit the MS Transmission Offset 265 ₁, 265 ₂, 265 ₃ to each BTS 210₁, 210 ₂, 210 ₃ as information included in the respective RLC data block270 ₁, 270 ₂, 270 ₃.

Each BTS 210 ₁, 210 ₂, 210 ₃ will perform a TA estimation 271 ₁, 271 ₂,271 ₃ based on the signal sent by the MS 204 (e.g., an access requestreceived on the EC-RACH or an uplink RLC data block received on anEC-PDTCH). In this process, the BTS 210 ₁, 210 ₂, 210 ₃ will estimatethe accuracy by which it is able to measure the timing of signalsreceived from the MS 204. From the accuracy (BTS timing advance accuracy271 ₁, 271 ₂, 271 ₃) estimated by the BTS 210 ₁, 210 ₂, 210 ₃ and theinformation (MS synchronization accuracy 264 ₁, 264 ₂, 264 ₃ and MSTransmission Offset 265 ₁, 265 ₂, 265 ₃) provided by the MS 204, a totalaccuracy of the TA estimation is derived. The BSS 202 ₁, 202 ₂, 202 ₃(BTS 210 ₁, 210 ₂, 210 ₃) can further use the MS Transmission Offset 265₁, 265 ₂, 265 ₃ to directly compensate the Estimated Timing Advance(TA_(estimated)) value 271 ₁, 271 ₂, 271 ₃ as this is a known error inthe MS 204, i.e., Adjusted Estimated Timing Advance(TA_(adjusted))=TA_(estimated)−MS Transmission Offset. Either of theseseparate accuracies or the total accuracy (i.e., the BTS processes thevalues of the BTS Timing Advance Accuracy 271 ₁, 271 ₂, 271 ₃ and the MSSync Accuracy 264 ₁, 264 ₂, 264 ₃ to arrive at a value for the overallTiming Advance Accuracy for the corresponding cell) is delivered by theserving BSS 202 ₁ to the serving SMLC node 206 ₁. The serving SMLC node206 ₁ combines accuracy estimates of TA estimates from multiple BTSs 210₁, 210 ₂, 210 ₃ to derive an estimate of the accuracy of the positioningof the MS 204.

It shall be noted to anyone skilled in the art that the principlesdescribed in the embodiments below also are applicable to other RadioAccess technologies such as Long Term Evolution (LTE), Universal MobileTelephony System (UMTS), Narrow Band Internet of Things (NB-IoT) andEnhanced Machine Type Communications (eMTC) where a communication device(a) estimates and adjusts (synchronizes) to the downlink timing of thenetwork and (b) the uplink transmission of the communication device whenaccessing the network may not be perfectly time aligned with the timingof the signals from the network as estimated during synchronization.

In a first embodiment of the present disclosure, it is proposed, inaddition to the Temporary Logical Link Identifier (TLLI) 274 (or otherMS identity) of the MS 204, to also include the estimated MSsynchronization accuracy 264 ₁ as well as the MS Transmission Offset 265₁ respectively in two new fields called MS Sync Accuracy field 278 andthe MS Transmission Offset field 290 in the Radio Link Control (RLC)data block 270 ₁ transmitted by the MS 204 on an uplink Temporary BlockFlow (TBF) established in response to an access request 272 indicatingMultilateration. In order for the BSS 202 ₁ (BTS 210 ₁) to extract theestimated MS synchronization accuracy 264 ₁ and the MS TransmissionOffset 265 ₁ from the uplink RLC data block 270 ₁, it is proposed thatthe MS 204 use a reserved length indicator 276, e.g., a length indicator276 of value 122 in the RLC data block 270 ₁ (note that any of theunused length indicators may be used). Length indicators are used todelimit upper layer PDU but may also be used to indicate the presence ofadditional information within the RLC data block. One example is thelength indicator with a value 125, which indicates the presence ofdynamic timeslot reduction control information which shall be includedafter the last Upper Layer PDU (see 3GPP TS 44.060 V13.3.0 (2016September)—the contents of which are incorporated by reference herein).In the case of Multilateration, it is proposed that a Length Indicator276 of value 122 be used in the RLC data block 270 ₁ by the MS 204 toindicate the presence of the MS synchronization accuracy field 278(which includes the estimated MS synchronization accuracy 264 ₁) and theMS Transmission Offset field 290 (which includes the MS TransmissionOffset 265 ₁) in the first octet immediately following the LengthIndicator 276. FIG. 4 is a diagram illustrating one possible coding ofthe MS synchronization accuracy field 278 which contains the MSestimated assessment of the BTS 210 ₁ timing (i.e., the MS estimatedsynchronization accuracy 264 ₁) in units of 1/32 of a symbol period.FIG. 5 is a diagram illustrating one possible coding of the MSTransmission Offset field 290 which contains the MS Transmission Offset265 ₁ which the MS 204 was forced to apply due to the transmissionopportunities corresponding to the internal base in units of 1/32 of asymbol period. An alternative coding or field realizations may also beused.

In a second embodiment, it is proposed, in addition to the TLLI 274 (orother MS identity) of the MS 204 and the Source Identity 280 of theServing BSS 202 ₁, to also include the estimated MS synchronizationaccuracy 264 ₂, 264 ₃ and the estimated uplink MS Transmission Offset265 ₂, 265 ₃ in the RLC data blocks 270 ₂, 270 ₃ transmitted by the MS204 on an uplink TBF established in response to an access request 272indicating Multilateration. In order for the BSSs 202 ₂, 202 ₃ (BTSs 210₂, 210 ₃) to extract the estimated MS synchronization accuracy 264 ₂,264 ₃ and the MS Transmission Offset 265 ₂, 265 ₃ from the uplink RLCdata blocks 270 ₂, 270 ₃, it is proposed that the MS 204 uses a reservedlength indicator 276, e.g., a length indicator 276 of value 122 withinthe RLC data blocks 270 ₂, 270 ₃. In the case of Multilateration, it isproposed that a Length Indicator 276 of value 122 is used in the RLCdata blocks 270 ₂, 270 ₃ by the MS 204 to indicate the presence of the“Source Identity” field 281, MS synchronization accuracy field 278, andthe MS Transmission Offset field 290 in the five octets immediatelyfollowing the Length Indicator 276 (four octets for the Source Identityfield 281, ½ octet for the MS synchronization accuracy field 278, and a½ octet for the MS Transmission Offset field 290). The assumption ofusing four octets for the Source Identity field 281 can be seen as validif it is always sufficient to provide two octets of Location Area Code(LAC) and two octets of Cell ID information for the source identity(i.e., if it can be assumed that only cells belonging to the same PublicLand Mobile Network (PLMN) are used for positioning). However, the“Source Identity” field 281 could alternatively comprise Mobile CountryCode (MCC)+Mobile Network Code (MNC)+LAC+Cell ID (i.e., a total of 7octets) in order to address the case where knowledge of PLMN ID(MCC+MNC) is needed to forward the derived TA information 264 ₂, 264 ₃and associated Cell ID information 280 from a non-serving BSS 202 ₂ and202 ₃ to the serving BSS 202 ₁. For possible codings of the MSsynchronization accuracy field 278 and the MS Transmission Offset field290, see FIGS. 4 and 5.

In either the first embodiment or the second embodiment, it is proposedthat the BSS 202 ₁, 202 ₂, 202 ₃ (BTS 210 ₁, 210 ₂, 210 ₃) or the SMLC206 ₁ uses the reported MS Transmission Offset 265 ₁, 265 ₂, 265 ₃ tocompensate the Estimated Timing Advance (TA_(estimated)) value 271 ₁,271 ₂, 271 ₃ to arrive at an Adjusted Estimated Timing Advance(TA_(adjusted)) value 285 ₁, 285 ₂, 285 ₃ according toTA_(adjusted)=TA_(estimated)−MS Transmission Offset 265 ₁, 265 ₂, 265 ₃.

In a third embodiment, in order to address a scenario when there is noassessment of the MS synchronization accuracy 264 ₁ and the MSTransmission Offset 265 ₁ from the MS 204 as the MTA procedure isperformed in each cell, it is proposed to add means for the serving BSS202 ₁ to pass a new field called the MS Transmission Timing AccuracyCapability IE 266 (which includes a total MS transmission accuracyderived from a worst case MS synchronization accuracy and a worst caseMS Transmission Offset) to the serving SMLC 206 ₁ in the BSSMAP-LEPERFORM LOCATION REQUEST message 269 sent from the serving BSS 202 ₁ tothe serving SMLC 206 ₁. In this case, the serving BSS 202 ₁ obtains theinformation carried in MS Transmission Timing Accuracy Capability IE 266from the MS Radio Access Capability Information Element (IE) 267received from the SGSN 207 when the SGSN 207 commands the BSS 202 ₁ toperform the positioning procedure. FIG. 6 illustrates details of theBSSMAP-LE PERFORM LOCATION REQUEST message 269 with the new MSTransmission Timing Accuracy Capability IE 266 (note: the reference toTABLE 9.1 3GPP TS 49.031 indicates that this table will be updated inthe new standard to reflect the updated BSSMAP-LE PERFORM LOCATIONREQUEST message 269 per the present disclosure). FIG. 7 illustratesdetails of the new MS Transmission Timing Accuracy Capability IE 266which is a variable length information element that is derived from aworst case MS synchronization accuracy and a worst case MS TransmissionOffset (note 1: the reference to 10.34 3GPP TS 49.031 indicates thatthis figure will be updated in the new standard to reflect the new MSTransmission Timing Accuracy Capability IE 266 per the presentdisclosure) (note 2: it is to be noted that the shown MS TransmissionTiming Accuracy Capability IE 266 is just an example and, to anyoneskilled in the art, various variations of the MS Transmission TimingAccuracy Capability IE 266 are possible such as a different range orthat a 4 bit field with smaller steps in granularity can be used). Forexample, if the worst case MS synchronization accuracy is ⅛ symbol andthe worst case MS Transmission Offset is ⅛ symbol, this results in atotal MS Transmission Timing Accuracy of ¼ symbol. Alternatively, theserving BSS 202 ₁ using a field 266 (MS Transmission Timing AccuracyCapability IE 266) that indicates the worst case synchronizationaccuracy of MS 204 and the worst case MS transmission offset is added tothe MS Radio Access Capability IE 267 which can be forwarded from theBSS 202 ₁ to the SMLC 206 ₁ as received by the BSS 202 ₁ from the SGSN207. FIGS. 8A-8B illustrate details of the MS Radio Access Capability IE267 with the new MS Transmission Timing Accuracy Capability IE 266(note: the reference to TABLE 10.5.146 3GPP TS 24.008 indicates thatthis table will be updated in the new standard to reflect the MSTransmission Timing Accuracy Capability IE 266 per the presentdisclosure). In yet another alternative, the complete MS Radio AccessCapability IE 267 is sent as a new IE in the BSSMAP-LE PERFORM LOCATIONREQUEST message 269 or the MS Transmission Timing Accuracy Capability IE266 is added to the Classmark Information Type 3 message alreadyoptionally included in the BSSMAP-LE PERFORM LOCATION REQUEST message269.

In a fourth embodiment, in order for the serving SMLC 206 ₁ to know theoverall accuracy of the estimation of the TA 271 ₁, 271 ₂, 271 ₃, it isproposed to add means for the BSS 202 ₁, 202 ₂, 202 ₃ (BTS 210 ₁, 210 ₂,210 ₃) to indicate an overall TA estimation accuracy to the serving SMLC206 ₁ in the BSSMAP-LE CONNECTION ORIENTED INFORMATION message 275 ₁,275 ₂, 275 ₃, either as a new IE or as part of the BSSLAP APDU. FIG. 9is a diagram that illustrates where a new 3GPP TS 49.031 MultilaterationTA (MTA) IE 277 is proposed to carry the overall Timing Advanceestimation accuracy (bits 2 to 4 of octet 2), which indicates theoverall timing advance estimation symbol granularity derived by the BSS202 ₁, 202 ₂, 202 ₃ taking its own TA accuracy (i.e., the BTS TimingAdvance Accuracy 271 ₁, 271 ₂, 271 ₃) as well as the MS estimatedaccuracy 264 ₁, 264 ₂, 264 ₃ of the timing of the BTS 210 ₁, 210 ₂, 210₃ (i.e., the estimated MS synchronization accuracy 264 ₁, 264 ₂, 264 ₃)into account. Alternatively, the same information could also have beenincluded in the BSSLAP APDU as a new 3GPP 48.071 Multilateration TimingAdvance (MTA) message.

Basic Functionalities-Configurations of the MS 204 and the BSS 202 ₁,202 ₂, 202 ₃

Referring to FIG. 10, there is a flowchart of a method 1000 implementedin the mobile station 204 that is configured to interact with BSS 202 ₁(the serving BSS 202 ₁) which includes BTS 210 ₁ (for example) inaccordance with an embodiment of the present disclosure. At step 1002,the mobile station 204 receives, from the BSS 202 ₁, a multilaterationrequest 272 (note: the serving SMLC 206 ₁ originally transmits themultilateration request 272 which is then transmitted by the BSS 202 ₁to the mobile station 204). At step 1004, the mobile station 204estimates a synchronization accuracy 264 ₁ with the BTS 210 ₁ andestimates a transmission offset 265 ₁ for uplink transmissions to theBTS 210 ₁ in response to receiving the multilateration request 272. Forinstance, the mobile station 204 can estimate the synchronizationaccuracy 264 ₁ with the BTS 210 ₁ by performing multiple timingmeasurements of the BTS 210 ₁ and estimating a variance between thetiming measurements of the BTS 210 ₁ (note: the variance can beestimated as discussed above with respect to equation nos. 1-3). Plus,the mobile station 204 can estimate the transmission offset 265 ₁ bytaking into account limitations of an internal time base and estimatedtiming of transmissions (e.g., with the SCH or the EC-SCH) from the BTS210 ₁ (see discussion above with respect to FIG. 3). At step 1006, themobile station 204 transmits, to the BSS 202 ₁, a RLC data block 270 ₁that includes at least (i) a TLLI 274 of the mobile station 204, (ii)the estimated synchronization accuracy 264 ₁, and (iii) the estimatedtransmission offset 265 ₁. The RLC data block 270 ₁ may further include(iv) a Source Identity 280 of the BSS 202 ₁, and (v) a length indicator276 to indicate a presence of the estimated synchronization accuracy 264₁ and the transmission offset 265 ₁. It should be appreciated that themobile station 204 would also perform at least steps 1004 and 1006 withthe non-serving BSSs 202 ₂ and 202 ₃.

Referring to FIG. 11, there is a block diagram illustrating structuresof an exemplary mobile station 204 in accordance with an embodiment ofthe present disclosure. In one embodiment, the mobile station 204comprises a receive module 1102, an estimate module 1104, and a transmitmodule 1106. The receive module 1102 is configured to receive from a BSS202 ₁ (for example) a multilateration request 272. The estimate module1104 is configured, in response to receipt of the multilaterationrequest 272, to estimate a synchronization accuracy 264 ₁ with the BTS210 ₁ and to estimate a transmission offset 265 ₁ for uplinktransmissions to the BTS 210 ₁. The transmit module 1106 is configuredto transmit, to the BSS 202 ₁, a RLC data block 270 ₁ that includes atleast (i) a TLLI 274 of the mobile station 204, (ii) the estimatedsynchronization accuracy 264 ₁, and (iii) the estimated transmissionoffset 265 ₁. The RLC data block 270 ₁ may further include (iv) a SourceIdentity 280 of the BSS 202 ₁, and (v) a length indicator 276 toindicate a presence of the estimated synchronization accuracy 264 ₁ andthe transmission offset 265 ₁. It should be noted that the mobilestation 204 may also include other components, modules or structureswhich are well-known, but for clarity, only the components, modules orstructures needed to describe the features of the present disclosure aredescribed herein.

As those skilled in the art will appreciate, the above-described modules1102, 1104, and 1106 of the mobile station 204 may be implementedseparately as suitable dedicated circuits. Further, the modules 1102,1104, and 1106 can also be implemented using any number of dedicatedcircuits through functional combination or separation. In someembodiments, the modules 1102, 1104, and 1106 may be even combined in asingle application specific integrated circuit (ASIC). As an alternativesoftware-based implementation, the mobile station 204 may comprise amemory 224, a processor 222 (including but not limited to amicroprocessor, a microcontroller or a Digital Signal Processor (DSP),etc.) and a transceiver 214. The memory 224 stores machine-readableprogram code executable by the processor 222 to cause the mobile station204 to perform the steps of the above-described method 1000.

Referring to FIG. 12, there is a flowchart of a method 1200 implementedin the BSS 202 ₁ (for example) which includes BTS 210 ₁ (for example)and is configured to interact with mobile station 204 and SMLC 206 ₁ inaccordance with an embodiment of the present disclosure. At step 1202,the BSS 202 ₁ transmits, to the mobile station 204, a multilaterationrequest 272 (note: the serving SMLC 206 ₁ originally transmits themultilateration request 272 which is then transmitted by the BSS 202 ₁to the mobile station 204). At step 1204, the BSS 202 ₁ receives, fromthe mobile station 204, a RLC data block 270 ₁ that includes at least(i) a TLLI 274 of the mobile station 204, (ii) an estimated mobilestation synchronization accuracy 264 ₁ (wherein the estimatedsynchronization accuracy 264 ₁ indicates an estimate by the mobilestation 204 of an accuracy by which the mobile station 204 issynchronized to the BTS 210 ₁), and (iii) a mobile station transmissionoffset 265 ₁ (wherein the mobile station transmission offset 265 ₁ isdetermined by the MS 204 by taking into account limitations of aninternal time base and estimated timing of transmissions from the BTS210 ₁). The RLC data block 270 ₁ may further include (iv) a SourceIdentity 280 of the BSS 202 ₁, and (v) a length indicator 276 toindicate a presence of the estimated synchronization accuracy 264 ₁ andthe transmission offset 265 ₁. At optional step 1206, the BSS 202 ₁obtains a BTS TA estimation 271 ₁ for the mobile station 204 calculatedby the BTS 210 ₁ based on the received RLC data block 270 ₁. At optionalstep 1208, the BSS 202 ₁ adjusts the BTS TA estimation 271 ₁ accordingto the mobile station transmission offset 265 ₁ (e.g., the BSS 202 ₁ canadjust the BTS TA estimation 271 ₁ per the following: the adjusted TAestimation (TA_(adjusted))=the TA estimation (TA_(estimated)) minus themobile station transmission offset 265 ₁). At optional step 1210, theBSS 202 ₁ transmits, to the SMLC 206 ₁, the adjusted BTS TA estimation285 ₁, the estimated mobile station synchronization accuracy 264 ₁, andthe BTS TA accuracy 273 ₁. It should be appreciated that the BSSs 202 ₂and 202 ₃ would also perform at least step 1204 with the mobile station204, and possibly optional steps 1206, 1208, and 1210.

Referring to FIG. 13, there is a block diagram illustrating structuresof an exemplary BSS 202 ₁ (for example) in accordance with an embodimentof the present disclosure. In one embodiment, the BSS 202 ₁ comprises afirst transmit module 1302, a receive module 1304, an optional obtainmodule 1306, an optional adjust module 1308, and an optional secondtransmit module 1310. The first transmit module 1302 is configured totransmit, to the mobile station 204, a multilateration request 272. Thereceive module 1304 is configured to receive, from the mobile station204, a RLC data block 270 ₁ that includes at least (i) a TLLI 274 of themobile station 204, (ii) an estimated mobile station synchronizationaccuracy 264 ₁ (wherein the estimated synchronization accuracy 264 ₁indicates an estimate by the mobile station 204 of an accuracy by whichthe mobile station 204 is synchronized to the BTS 210 ₁), and (iii) amobile station transmission offset 265 ₁ (wherein the mobile stationtransmission offset 265 ₁ is determined by the MS 204 by taking intoaccount limitations of an internal time base and estimated timing oftransmissions from the BTS 210 ₁). The RLC data block 270 ₁ may furtherinclude (iv) a Source Identity 280 of the BSS 202 ₁, and (v) a lengthindicator 276 to indicate a presence of the estimated synchronizationaccuracy 264 ₁ and the transmission offset 265 ₁. The optional obtainmodule 1306 is configured to obtain a BTS TA estimation 271 ₁ for themobile station 204 calculated by the BTS 210 ₁ based on the received RLCdata block 270 ₁. The optional adjust module 1308 is configured toadjust the BTS TA estimation 271 ₁ according to the mobile stationtransmission offset 265 ₁ (e.g., the BSS 202 ₁ can adjust the BTS TAestimation 271 ₁ per the following: the adjusted TA estimation(TA_(adjusted))=the TA estimation (TA_(estimated)) minus the mobilestation transmission offset 265 ₁). The optional second transmit module1310 is configured to transmit, to the SMLC 206 ₁, the adjusted BTS TAestimation 285 ₁, the estimated mobile station synchronization accuracy264 ₁, and the BTS TA accuracy 2′731. It should be noted that the BSS202 ₁ may also include other components, modules or structures which arewell-known, but for clarity, only the components, modules or structuresneeded to describe the features of the present disclosure are describedherein.

As those skilled in the art will appreciate, the above-described modules1302, 1304, 1306, 1308, and 1310 of the BSS 202 ₁ may be implementedseparately as suitable dedicated circuits. Further, the modules 1302,1304, 1306, 1308, and 1310 can also be implemented using any number ofdedicated circuits through functional combination or separation. In someembodiments, the modules 1302, 1304, 1306, 1308, and 1310 may be evencombined in a single application specific integrated circuit (ASIC). Asan alternative software-based implementation, the BSS 202 ₁ may comprisea memory 250 ₁, a processor 248 ₁ (including but not limited to amicroprocessor, a microcontroller or a Digital Signal Processor (DSP),etc.) and a transceiver 238 ₁. The memory 250 ₁ stores machine-readableprogram code executable by the processor 248 ₁ to cause the BSS 202 ₁ toperform the steps of the above-described method 1200. Note: the otherBSSs 202 ₂ and 202 ₃ may be configured the same as BSS 202 ₁.

In view of the foregoing disclosure, it will be readily appreciated thatit is beneficial for the serving SMLC 206 ₁ to receive cell specifictiming advance information that is supplemented with MS SynchronizationAccuracy information 264 ₁, 264 ₂, 264 ₃ that indicates the guaranteedminimum accuracy with which the MS 204 is able to synchronize to signalsreceived from the BTS 210 ₁, 210 ₂, 210 ₃ and time its uplinktransmissions accordingly. It should also be appreciated that anotherproblem addressed herein by the disclosed techniques is that thepossible timing of MS 204 uplink transmissions may be restricted by theMS implementation, e.g., by an internal time base to which uplinktransmissions made by the MS 204 must be aligned, and whose phase cannotbe adjusted. This means that MS 204 implementations that force uplinktransmissions to align with such an internal time base will commonlyresult is an offset in the timing of the MS transmissions, relative to(case a) the estimated timing of the signals received from the BTS 210₁, 210 ₂, 210 ₃ for the case of e.g., an access attempt sent on theRandom Access Channel (RACH)/Extended Coverage-Random Access Channel(EC-RACH) or (case b) the timing advance information sent from a BSS 202₁, 202 ₂, 202 ₃ to an MS 204 in response to e.g., an access request sentby the MS 204 on the RACH/EC-AGCH. In other words, MS uplinktransmissions will not be made according to the MS SynchronizationAccuracy 264 ₁, 264 ₂, 264 ₃ alone per (case a) according to the MSSynchronization Accuracy 264 ₁, 264 ₂, 264 ₃ plus an indicated timingadvance as per (case b), but may also be subject to an offset, hereincalled the MS Transmission Offset 265 ₁,265 ₂, 265 ₃, that the MS 204 isaware of but unable to correct. Further, the BTS 210 ₁, 210 ₂, 210 ₃ (orthe SMLC 206 ₁) can use the MS Transmission Offset 265 ₁, 265 ₂, 265 todirectly compensate the Estimated BTS Timing Advance value 271 ₁, 271 ₂,271 ₃ in order to derive a more accurate value referred to herein as anAdjusted BTS Estimated Timing Advance value 285 ₁, 285 ₂, 285 ₃. As suchit will be beneficial for the BTS 210 ₁, 210 ₂, 210 ₃ to receive “MSTransmission Offset” information 265 ₁, 265 ₂, 265 ₃ from the MS 204whenever it performs the positioning procedure in a given cell, therebyallowing e.g., the BTS 210 ₁, 210 ₂, 210 ₃ to adjust its “EstimatedTiming Advance” 271 ₁, 271 ₂, 271 ₃ for that MS 204 so that an “AdjustedEstimated Timing Advance” 285 ₁, 285 ₂, 285 ₃ can be determined andrelayed to the serving SMLC 206 ₁.

Those skilled in the art will appreciate that the use of the term“exemplary” is used herein to mean “illustrative,” or “serving as anexample,” and is not intended to imply that a particular embodiment ispreferred over another or that a particular feature is essential.Likewise, the terms “first” and “second,” and similar terms, are usedsimply to distinguish one particular instance of an item or feature fromanother, and do not indicate a particular order or arrangement, unlessthe context clearly indicates otherwise. Further, the term “step,” asused herein, is meant to be synonymous with “operation” or “action.” Anydescription herein of a sequence of steps does not imply that theseoperations must be carried out in a particular order, or even that theseoperations are carried out in any order at all, unless the context orthe details of the described operation clearly indicates otherwise.

Of course, the present disclosure may be carried out in other specificways than those herein set forth without departing from the scope andessential characteristics of the invention. One or more of the specificprocesses discussed above may be carried out in a cellular phone orother communications transceiver comprising one or more appropriatelyconfigured processing circuits, which may in some embodiments beembodied in one or more application-specific integrated circuits(ASICs). In some embodiments, these processing circuits may comprise oneor more microprocessors, microcontrollers, and/or digital signalprocessors programmed with appropriate software and/or firmware to carryout one or more of the operations described above, or variants thereof.In some embodiments, these processing circuits may comprise customizedhardware to carry out one or more of the functions described above. Thepresent embodiments are, therefore, to be considered in all respects asillustrative and not restrictive.

Although multiple embodiments of the present disclosure have beenillustrated in the accompanying Drawings and described in the foregoingDetailed Description, it should be understood that the invention is notlimited to the disclosed embodiments, but instead is also capable ofnumerous rearrangements, modifications and substitutions withoutdeparting from the present disclosure that as has been set forth anddefined within the following claims.

1. A base station subsystem (BSS) configured to interact with a mobilestation and a Serving Mobile Location Center (SMLC), wherein the BSSincludes a base transceiver station (BTS), the BSS comprising: aprocessor; and, a memory that stores processor-executable instructions,wherein the processor interfaces with the memory to execute theprocessor-executable instructions, whereby the BSS is operable to:transmit, to the mobile station, a multilateration request; and,receive, from the mobile station, a Radio Link Control (RLC) data blockthat includes at least (i) a Temporary Logical Link Identifier (TLLI) ofthe mobile station, (ii) an estimated mobile station synchronizationaccuracy, and (iii) a mobile station transmission offset.
 2. The BSS ofclaim 1, wherein the BSS is further operable to: obtain a timing advance(TA) estimation for the mobile station calculated by the BTS based onthe received RLC data block; adjust the TA estimation according to themobile station transmission offset; and transmit, to the SMLC, theadjusted TA estimation, the estimated mobile station synchronizationaccuracy, and a BTS TA accuracy.
 3. The BSS of claim 2, wherein the BSSperforms the adjust operation per the following: the adjusted TAestimation (TA_(adjusted))=the TA estimation (TA_(estimated)) minus themobile station transmission offset.
 4. The BSS of claim 1, wherein theRLC data block further includes a Source Identity of the BSS.
 5. The BSS of claim 1, wherein the RLC data block further includes a lengthindicator to indicate a presence of the estimated mobile stationsynchronization accuracy and the mobile station transmission offset. 6.A method in a base station subsystem (BSS) configured to interact with amobile station and a Serving Mobile Location Center (SMLC), wherein theBSS includes a base transceiver station (BTS), the method comprising:transmitting, to the mobile station, a multilateration request; and,receiving, from the mobile station, a Radio Link Control (RLC) datablock that includes at least (i) a Temporary Logical Link Identifier(TLLI) of the mobile station, (ii) an estimated mobile stationsynchronization accuracy, and (iii) a mobile station transmissionoffset.
 7. The method of claim 6, further comprising: obtaining a timingadvance (TA) estimation for the mobile station calculated by the BTSbased on the received RLC data block; adjusting the TA estimationaccording to the mobile station transmission offset; and transmitting,to the SMLC node, the adjusted TA estimation, the estimated mobilestation synchronization accuracy, and a BTS TA accuracy.
 8. The methodof claim 7, wherein the adjusting step is performed as follows: theadjusted TA estimation (TA_(adjusted))=the TA estimation(TA_(estimated)) minus the mobile station transmission offset.
 9. Themethod of claim 6, wherein the RLC data block further includes a SourceIdentity of the BSS.
 10. The method of claim 6, wherein the RLC datablock further includes a length indicator to indicate a presence of theestimated mobile station synchronization accuracy and the mobile stationtransmission offset.